Rumors of Wars
A Brief Discussion of
Just War Theory

By Gabriel Blanchard

Few topics are as theoretically involved, or as grimly practical, as the ethical philosophy of violence.

Unrest in places such as Ukraine and the Holy Land have once again brought forward the thorny and mutually entangled topics of states, the stateless, and all conflict and violence. CLT is committed to remaining politically non-partisan. However, war and the philosophical knots it ties us in are a familiar subject in classic literature, and a principal reason we promote that literature is that we believe it gives us tools to pursue justice and truth in our own place and time. We’d therefore like to offer our readers a brief introduction to just war theory.

The Ethical Problem of Violence

To begin with first principles: violence is bad. Under specific circumstances, violence of some kind might be the best course of action available, but it is not something we want in itself. Since the epoch of the caveman, when Gurk first hit Thag on head with rock and Thag had a bad time, we have all been eager not to be Thag in that equation.

Thag has about six possible reactions to Gurk at his disposal—two violent, one a bit ambiguous, and three non-violent:

  1. Aggression (hit Gurk in the head with a rock first);
  2. Retribution (hit Gurk in the head with a rock back);
  3. Self-defense (block Gurk’s rock—perhaps with Thag’s rock);
  4. Diplomacy (tell Gurk not to hit Thag on the head with a rock till Gurk agrees);
  5. Flight (hide or run away from Gurk); or
  6. Inaction (do nothing).

How do these options map to right and wrong? That Gurk ought not hit Thag is true; but once he has—well, they do say the past is set in rock. Many arguments have been advanced for and against all six reactions. Here, we must content ourselves with a basic outline of just war theory, which (while by no means universal) is the most widely accepted view in our tradition.

The Background

We know little of the Gurk vs. Thag period of humanity, but as soon as we reach history proper, we find restrictions on violence. Ancient China produced a large literature on warfare during the late Zhou dynasty (ca. 450-200 BC); India’s national epic, the Mahābhārata,* discusses topics like noncombatant immunity and proportional force. For once, ancient Greece was apparently late to the intellectual party! The Homeric epics depict a Mycenæan Greek culture driven by κλέος [kleos], or “renown”—more like half-cartoon Vikings than sedate, toga-clad sages.** In any case, whether Aristotle borrowed the idea from elsewhere or came up with it independently, we find a basic statement of just war theory in Book VII of the Politics; and by the time the Romans dropped by to have a quick conquest of Greece, they had had generations of jurists writing treatises on the jus gentium or “law of peoples,”—which laid out among other things why the Romans should not really do things like have a quick conquest of Greece.

A turning point came with the Christianization of the Roman Empire.† Western civilization proposed to become Christendom, a society organized upon the Christian religion, which commended pardon over vengeance, love over hatred of enemy, sharing over hoarding resources, modesty over renown, placing one’s own interests last rather than first. Yet these ideals seem to reflexively endanger the project of Christendom: could a civilization organized on them defend itself? As the West Roman Empire disintegrated and Medieval Europe took shape, Christian scholars—rightly or wrongly—tried to strike a balance between the social urge to be ruled and protected by law, and the “more excellent way” commended by the New Testament. This developed further in the Middle Ages, especially under the influences of the code of chivalry, Scholasticism, and the sixteenth-century School of Salamanca. A few important figures in this development include St. Augustine, St. Thomas Aquinas, Bartolomé de Las Casas, Hugo Grotius, Carl von Clausewitz, and Mahatma Gandhi. It is through these developments that we get classic just war theory.

Let me have eyes I need not shut;
Let me have truth at my tongue's root;
Let courage and the brain command
The honest fingers of my hand;
And when I wait to save my skin
Break roof and let my death come in.

Classic Just War Theory …

Just war theorists set forth a system of criteria that justify the use of violence, up to and including war, if all of them are met. These conditions fall under two main headings: jus ad bellum, or “the right to [resort to] war”; and jus in bello, or “right in [waging] war.” Lists vary slightly from one theorist to another. However, criteria for jus ad bellum virtually always include:

  1. Just cause. Aggressive warfare is always off the table. Acquiring new territories or resources—or even reclaiming old ones—is not a just cause; neither are “punitive expeditions” to avenge feigned or real injuries. Only wars fought in self-defense or the defense of an ally can be justified.
  2. Probability of success. There must be a reasonable likelihood that the defense will succeed. Otherwise, the war effort is throwing lives away to no purpose.
  3. Last resort. All nonviolent means of avoiding or resolving the conflict must be attempted first, or else shown to be clearly unfeasible. Only when all nonviolent resolutions have failed does war become permissible.
  4. Declaration by competent authority. Wars must be publicly declared; moreover, this must be done by lawfully appointed leaders of the state. (Those who have usurped the reins of power are not necessarily qualified, nor lesser officials).

If any one of these conditions has not been met, no right to wage war exists.

Typical criteria for jus in bello are along these lines:

  1. Distinction of non-combatants. All non-combatants—civilians, medics, the wounded, enemy prisoners, all—must be treated as sacrosanct. While a limited amount of unintentional “collateral damage” is usually tolerated by just war theorists, tactics that target noncombatants (especially the civilian population) are among the gravest possible violations of this rule.
  2. Proportionality. Force can be permissible, but there is still such a thing as going too far. How much force may be used, and of what kind, depends on what is necessary to effect the defense you have mounted (though most theorist would allow that offensive campaigns can be part of a just war). The fact or rumor that the enemy has used a tactic does not ipso facto make it permissible, and reprisals are illicit, no matter how the enemy conduct themselves.
  3. Humanity. The word humanity here does not mean our species, but the quality of being humane, i.e. showing empathy rather than cruelty. Means that are malum in se [evil in themselves] are absolutely forbidden. Such tactics are those have no exclusively defensive purpose; examples include genocide, mass rape, and the use of arms that have uncontrollable effects, like nuclear or biological weapons.

Some theorists list further criteria, and not every thinker categorizes the principles quite the same way. However, this is a fairly representative list of requirements for jus ad bellum and in bello.

… And Its Discontents

As said before, just war theory is probably the most common opinion within our intellectual tradition. However, it has plenty of critics and difficulties, and has done for centuries. We will briefly sketch only four.

  1. Are there any conditions for jus post bello, i.e how to justly end a war? Wars normally end either by one side defeating the other or a compromise being brokered between the parties. However, the conclusions of the world wars raised considerable doubt about whether the terms imposed by the Allies upon their foes were just—especially since the lopsidedness of the 1919 Treaty of Versailles contributed directly to the rise of the Nazi Party. Moreover, the trials of Nazi leadership by an international court were unprecedented at the time; and the Allied demand for specifically unconditional surrender from Japan seems to clash with the requirements of humanity and proportionality. No general consensus has yet been reached on whether jus post bello is properly part of just war theory, or what it consists in, if so.
  2. Can just war theory be applied to non-state aggressors? This has come up chiefly in the context of terrorism. Going to war against another state is more straightforward: its territory is definite and its leadership (or at the least its head) is public knowledge, domestically and abroad. Terrorist organizations are defined by ideological goals, not geography, and both membership and leaders are frequently secret. It is quite difficult to see how to apply just war principles to terrorist groups.
  3. Can any war, but especially modern wars, satisfy the conditions of just war theory? Seven requirements are laid out above for jus ad bellum and jus in bello; very few wars, if any, have ever met them, and some theorists doubt whether the conditions are of real use. (Interestingly, these doubts come both from “hawks” who seem irked by the restrictions, and “doves” who dislike any rationale for war.) Moreover, many modern forms of warfare—chemical, nuclear, biological—have no hope of passing the malum in se prohibition, and yet to forego them seems to invite rapid defeat at the hands of any less-scrupulous enemy. Under such conditions, is there any point in pursuing just war theory?
  4. Is nonviolence a truly viable alternative? It is common to greet this question with derision or even anger. To suggest meeting a gun or a bomb with nothing sounds to many people like suicide, especially right after the unprecedented bloodshed of the twentieth century, claiming hundreds of millions of lives. And yet, in the middle of that same century, we find two nonviolent efforts—the Indian Swaraj campaign led by Mahatma Gandhi, and the civil rights movement in the US led by Martin Luther King Jr. and others—that were not mown down, and more than that, actually achieved their main goals. Pacifism has long been advanced on ethical grounds; pacifism as, counter-intuitively, a winning strategy seems to merit further analysis. This would in turn impact just war theory, especially the criterion of last resort.

Suggested reading:
Jiang Ziya, The Three Strategies of Huang Shigong
Homer, the Iliad
St. Augustine, De Civitate Dei [“On the City of God”]
The Trial of Joan of Arc (trans. from French and Latin by W. P. Barrett)
Desiderius Erasmus, The Complaint of Peace
Hugo Grotius, De Jure Belli ac Pacis [“The Law of War and of Peace”]
Henry David Thoreau, Resistance to Civil Government (or Civil Disobedience)
Vladimir Lenin, Imperialism, the Highest Stage of Capitalism
Mahatma Gandhi, Satyagraha in South Africa
The Geneva Conventions and Protocols

*I.e. “Bharata the Great,” likely referring to the mythic Emperor Bharata who ruled the earth for twenty-seven thousand years (his descendants are principal characters in the epic). The Mahābhārata is the longest poem known to exist, about fifteen times the length of the Bible.
**The real history is likely a bit more complicated. The Homeric period had lost some knowledge of the Bronze Age, so it may distort Mycenæan values, and Greece already had far-flung commerce in the second millennium BC, which could have introduced ethical theories of war. Additionally, we cannot read Linear A—the Minoan script—and thus do not know what it may preserve. (Then again, the related Mycenæan script of Linear B turned out to consist mostly of receipts.)
†Primitive Christianity (up to the legalization of 313) was, at least apparently, pacifistic. Besides texts like the Sermon on the Mount and the early martyrologies, books on pastoral policy call for prospective converts among soldiers to be refused unless they find a nonviolent role to play, and for present Christians who enter the military to be excommunicated. This remained normal for centuries.


Gabriel Blanchard came to work for CLT in 2019, and serves as the company’s editor at large. He lives in Baltimore, MD.

Thank you for reading the Journal; if you’d like to read more on this subject, our Great Conversation series includes posts on judgment, life and death, and revolution. You might also enjoy our podcast, Anchored, hosted by CLT’s founder, Jeremy Tate.

Published on 2nd November, 2023. Page image of The Battle of Alexander at Issus (1529) by Albrecht Altdorfer, depicting a crucial victory of Alexander the Great over Darius III in 333 BC; this led to the destruction of the Achæmenid Persian Empire and establishing a Greek cultural presence as far east as the Indus River (in modern Pakistan), maintained for centuries by the Seleucid and later Roman Empires.

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